Method and apparatus for testing phase shifter modules of a phased array

Abstract

Faulty subarray module circuit boards are detected in a phased array antenna having many subarray module circuit boards while the antenna is fully assembled and operationally integrated with a radar system. A far field ratio frequency test source illuminates the antenna. Binary digital signals that control subarray steering bits are set to a reference setting. A particular subarray module circuit board that is under test has its 180.degree. main phase bit toggled between 0.degree. and 180.degree.. The radar selects the output of that particular subarray module by Doppler filter type of software filtering. The amplitude of the in-phase and quadrature phase signals from the radar is recorded. The binary digital signals that control subarray steering bits are set to a second setting. The 180.degree. main phase bit of the module under test is again toggled between 0.degree. and 180.degree.. The output of the module under test is again selected by Doppler filter type of software filtering. The amplitude of the in-phase and quadrature phase signals from the radar is recorded. The phase difference from the reference setting to the second setting is computed and compared with a predetermined threshold. If desired, the test source may have a multi-element feed including multiple dipoles, each dipole having a radiation pattern wide enough to cover two rows of subarray modules, the test source being switched to the particular one of the dipoles that illuminates the row including the module under test.